redis-py New `asyncio.exceptions.CancelledError` from 4.5.2

The Fix

pip install redis==7.1.0

Based on closed redis/redis-py issue #2633 · PR/commit linked

Production note: Watch p95/p99 latency and retry volume; timeouts can turn into retry storms and duplicate side-effects.

Jump to Verify Open PR/Commit

@@ -546,6 +546,7 @@ def __del__(
             except RuntimeError:
                 pass
+            self.connection._close()
 
     async def aclose(self, close_connection_pool: Optional[bool] = None) -> None:

repro.py

from collections.abc import Callable, Awaitable

import redis.asyncio
from fastapi import FastAPI, APIRouter, Request, Response
from httpx import AsyncClient
from starlette.middleware.base import BaseHTTPMiddleware


class DummyMiddleware(BaseHTTPMiddleware):
    async def dispatch(
        self,
        request: Request,
        call_next: Callable[[Request], Awaitable[Response]],
    ) -> Response:
        return await call_next(request)


@pytest.mark.asyncio
async def test_redis() -> None:
    app = FastAPI()
    app.add_middleware(DummyMiddleware)

    @app.get("/")
    async def index() -> dict[str, str]:
        return {}

    async with AsyncClient(app=app, base_url="https://example.com/") as client:
        await client.get("/")
        pool = redis.asyncio.from_url("redis://localhost:6379/0")
        await pool.set("key", "value")

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install redis==7.1.0\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n

Why This Fix Works in Production

Trigger: without_httpx
Mechanism: Fixes the issue of `CancelledError` being raised in asyncio calls by ensuring that the correct timeout library is used for Python versions 3.11.3 and above.
Why the fix works: Fixes the issue of `CancelledError` being raised in asyncio calls by ensuring that the correct timeout library is used for Python versions 3.11.3 and above. (first fixed release: 7.1.0).

Production impact:

If left unfixed, tail latency can spike under load and surface as timeouts/retries (amplifying incident impact).

Why This Breaks in Prod

Triggered by an upgrade/regression window: 3.11.3 breaks; 7.1.0 is the first fixed release.
Dependency interaction matters here: httpx v0.27.0.
Shows up under Python 3.11.2 in real deployments (not just unit tests).
Surfaces as: without_httpx

Proof / Evidence

GitHub issue: #2633
Fix PR: https://github.com/redis/redis-py/pull/2999
First fixed release: 7.1.0
Affected versions: 3.11.3
Reproduced locally: No (not executed)
Last verified: 2026-02-07
Confidence: 0.75
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.25

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“To everyone here, I think I found the culprit”

@bellini666 · 2023-03-23 · repro detail · source

“@curtiscook Yes, this issue fixed in in 4.5.4 (#2659)”

@dvora-h · 2023-04-30 · confirmation · source

“> * just closed, then reopen”

@curtiscook · 2023-03-23 · confirmation · source

“@sileht I have created a minimal reproduction example using httpx and [email protected] Running it will result in: Testing with 4.5.2 also gives the same error,…”

@bellini666 · 2023-03-23 · repro detail · source

Failure Signature (Search String)

without_httpx

Error Message

Stack trace

error.txt

Error Message
-------------
without_httpx
b'1'
b'2'
with_httpx_sync
b'1'
{'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-httpx/0.23.3', 'X-Amzn-Trace-Id': 'Root=1-641c81d6-2e145a8c4ca1ee0a178c2573'}, 'origin': '45.4.34.79', 'url': 'https://httpbin.org/get'}
b'2'
without_httpx_async
b'1'
{'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-httpx/0.23.3', 'X-Amzn-Trace-Id': 'Root=1-641c81d6-3ec88c7b5bd6013d2201d553'}, 'origin': '45.4.34.79', 'url': 'https://httpbin.org/get'}
Traceback (most recent call last):
  File "/tmp/xxx/test.py", line 46, in <module>
    asyncio.run(main())
  File "/home/bellini/.local/share/rtx/installs/python/3.11.2/lib/python3.11/asyncio/runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/home/bellini/.local/share/rtx/installs/python/3.11.2/lib/python3.11/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/bellini/.local/share/rtx/installs/python/3.11.2/lib/python3.11/asyncio/base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/tmp/xxx/test.py", line 42, in main
    await with_httpx_async()
  File "/tmp/xxx/test.py", line 33, in with_httpx_async
.
... (truncated) ...

Stack trace

error.txt

Error Message
-------------
Using python3.11 (3.11.8)
without_httpx
b'1'
b'2'
with_httpx_async
b'1'
{'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-httpx/0.27.0', 'X-Amzn-Trace-Id': 'Root=1-660b04d4-0ed17ec26d7b388724aaf03b'}, 'origin': '212.85.182.26', 'url': 'https://httpbin.org/get'}
Traceback (most recent call last):
  File "/mnt/d/Development/Infold/assembler/asyn_bug.py", line 35, in <module>
    asyncio.run(main())
  File "/usr/lib/python3.11/asyncio/runners.py", line 188, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/runners.py", line 120, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/asyncio/base_events.py", line 650, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/mnt/d/Development/Infold/assembler/asyn_bug.py", line 31, in main
    await with_httpx_async()
  File "/mnt/d/Development/Infold/assembler/asyn_bug.py", line 23, in with_httpx_async
    print(await conn.get("bar"))
          ^^^^^^^^^^^^^^^^^^^^^
  File "/home/naltharial/.cache/pypoetry/virtualenvs/assembler-01ENdme1-py3.11/lib/python3.11/site-packages/redis/asyncio/client.py", line 605, in execute_command
    conn = self.connection or await pool.get_connection(command_name, **options)
... (t
... (truncated) ...

Minimal Reproduction

repro.py

from collections.abc import Callable, Awaitable

import redis.asyncio
from fastapi import FastAPI, APIRouter, Request, Response
from httpx import AsyncClient
from starlette.middleware.base import BaseHTTPMiddleware


class DummyMiddleware(BaseHTTPMiddleware):
    async def dispatch(
        self,
        request: Request,
        call_next: Callable[[Request], Awaitable[Response]],
    ) -> Response:
        return await call_next(request)


@pytest.mark.asyncio
async def test_redis() -> None:
    app = FastAPI()
    app.add_middleware(DummyMiddleware)

    @app.get("/")
    async def index() -> dict[str, str]:
        return {}

    async with AsyncClient(app=app, base_url="https://example.com/") as client:
        await client.get("/")
        pool = redis.asyncio.from_url("redis://localhost:6379/0")
        await pool.set("key", "value")

Environment

Python: 3.11.2
httpx: 0.27.0

What Broke

Users experience uncaught CancelledError when writing to Redis using asyncio.

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install redis==7.1.0

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/redis/redis-py/pull/2999

First fixed release: 7.1.0

Last verified: 2026-02-07. Validate in your environment.

When NOT to Use This Fix

Do not use if it changes public behavior or if the failure cannot be reproduced.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Add a stress test that runs high-concurrency workloads and fails on thread dumps / blocked locks.
Enable watchdog dumps in prod (faulthandler, thread dump endpoint) to capture deadlocks quickly.
Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Version Compatibility Table

Version	Status
3.11.3	Broken
7.1.0	Fixed

Related Issues

No related fixes found.

Cluster: redis-py:timeout redis-py hub redis-py best practices All hubs All clusters

Related clusters: Configuration error Retry storm Data consistency

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

redis-py New `asyncio.exceptions.CancelledError` from 4.5.2 (Fix)